tonight in syria, the city of aleppo, their new york city, four car bombs killed nearly 40 people. eyewitnesses describe what felt like a series of earthquakes, giant buildings flattened. and here, a square before and after, you can see there, reduced to rubble. >>> and, in iran, something we rarely see. clashes in the streets of tehran, as hundreds of protesters take on their own government. outraged over the collapse of the iranian currency. it's taken a nose dive in the past week, down 40%. and that is a record low. and that is proof, economists say, that tough sanctions by the u.s. government, because of iran's nuclear program, are taking hold. >>> and now, we turn to a headline that sounded impossible to us today. word of yet another american airlines flight forced to land. passengers bracing for impact. in the end, the landing gear came down, but some suspicious passengers are telling us they actually wonder if pilots and other employees are negotiating their labor disputes from 30,000 feet. abc's senior national correspondent jim avila put that question to a pilot who believ